Greetings. You're about to embark on a journey that will suck away your life as you know it. You won't be left with a void. Quite the contrary -- your life will be filled with ideas, projects, and pressures. You'll sink or swim, learning skills that you previously thought were just for MBA types (oh, project management is critical; negotiation skills are useful; strategic partnerships often essential).
So sleep well these next few days, and enjoy the end of your freedom. You likely won't have a guilt-free day off/holiday/vacation/etc. for several years. Some folks who walk down this path never see one of those days again.
Things are a little different in the humanities -- philosophers work in collaborative teams much less often than social scientists do -- but the second sentence and second paragraph really struck home. This guilt is especially bad during Spring Break: I will get to sleep in, but I can't shake the feeling that I should be doing research for a paper, or at least working on my latest 'extracurricular' philosophy book. Since I'd rather do something that's both fun and relaxing, I end up bored and watching too much teevee all week.
It isn't really a bad career, and, in fact, the feeling of always having more to think about is part of what attracts me to academia. It's just that -- and I suspect this is the same with doctors -- the pressure to constantly be highly productive, to always actively engage that stuff you haven't thought about yet, makes it extremely difficult to enjoy not being productive during your vacations.